"Although the prophecy of the Neviim, which is apparition and vision, have been removed, the prophecy of the Chachamim, which is through wisdom, has not been removed, rather they know the truth through the Ruach HaKodesh which is inside them" (Ramban Bava Basra 12a)

"You should know, that this matter was accepted by the Tzaddikim, and not one denied it, that Hakadosh Baruch Hu shows the Tzaddikim awesome sights similar to His showing the Neviim." (Rav Hai Gaon, brought in "HaKosev" to Ein Yaakov Chagiga, Chapter 2)

"Eliyahu HaNavi still lives, concealing and revealing himself in each and every generation to the Tzaddikim who merit it,... until the complete redemption, he wanders in this world among the Tzadikim and the Chassidim" (Beis Elokim of the Mabit, Shaar HaYesodos, Chapter 60)

"A great fundamental of the Torah and a root of Emunah, which is a derivative of belief in Providence, is that Hashem forces nature under the feet of the believers... and if one has a doubt that Hashem will not perform the will of the Navi or the Tzaddik or the Chassid who is worthy, he is as one who places doubt in the Torah and in a root of its roots" (Sefer HaIkarim, Maamar IV, Perek 22)

"We are obligated to believe, in the novelty of a sign and wonder, at a time when necessary, in the entire world, through a prophet or even one of the Chassidim; and this matter continues on from fathers to sons" (Rashba, brought in "HaKosev" to Ein Yaakov Chullin 81a)